1. Field of the Invention
The present invention relates to a vibration damping device and more particularly it relates to a vibration damping device adapted to consume kinetic energy produced when a building or apparatus is moved by a vibration input, such as earthquakes, winds, traffic vibrations or mechanical vibrations, attended by an energy loss which means attainment of absorption and suppression of the vibrations in such building or apparatus.
2. Related Art
In the case of protecting buildings or apparatuses from various vibrations such as earthquakes, winds, traffic vibrations and mechanical vibrations, various types of vibration suppressing devices, such as earthquake proofing devices, are used. For example, an earthquake proofing device protects a building or apparatus when a vibration occurs by imparting a resonance frequency sufficiently higher than the input frequency. In this case, it has been common practice to use a vibration damping device, such as an oil damper, friction damper or hysteresis damper, as well.
Besides being used together with said earthquake proofing devices, such vibration damping devices, including oil dampers, friction dampers and hysteresis dampers, are singly used as vibration suppressing devices to absorb kinetic energy due to various vibrations, such as earthquakes, winds, traffic vibrations and mechanical vibrations.
The present applicant previously proposed a vibration suppressing device disclosed in Japanese Patent Application Publication (Kokat) No. Hei 3-217533. This device comprises a plurality of rolling bodies interposed between an upper structure and a lower structure to horizontally swingably support said upper structure, rolling surfaces for said rolling bodies having elastomeric members disposed thereon, the arrangement being such that the rolling of said rolling bodies absorbs the horizontal component of vibration energy while the local elastic deformation of the elastomeric members forming the rolling surfaces absorb the vertical component of vibration energy.
In this connection it is to be noted that a vibration damping device used as a vibration suppressing device has to be designed to develop the desired damping characteristics associated with the manner of use, and in this respect the vibration suppressing device disclosed in Japanese Patent Application Publication No. Hei 3-217533 is adapted to change its damping performance by changing the kind of material or thickness of the elastomeric members, supported load or the diameter of the rolling bodies.
Even if the kind of material or thickness of the elastomeric members, supported load or the diameter of the rolling bodies is changed, however, it is difficult to change the damping performance to a great degree and the degree of freedom of design of damping performance is low, making it difficult to attain the proper manner of use.